Aliexpress
Click here… to search for JHEMCU SIF4 F4 Flight Controller 13A Blheli_S 2-4S ESC + 40CH VTX on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (34.01 USD): BGAFF10OFF
Coupon (34.77 USD): Parts8
(CouponsFromChina.com tip: just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGSIF4, AFfbG10, BG12MRP, BGGEPPart, BGVDay10%off, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for JHEMCU SIF4 F4 Flight Controller 13A Blheli_S 2-4S ESC + 40CH VTX.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).